Field of the Invention
The present invention relates to a printing mechanism having a mandrel and a sleeve to be mounted on the mandrel. More particularly, the present invention relates to a printing mechanism having a mandrel and a variety of sleeves having outer peripheral surface to which printing plates are attached.
Description of the Related Arts
Conventionally, as a method of mounting a printing plate on a mandrel of a printing mechanism, there has been such a widely used method that a thin plate cylinder (sleeve) having the same length as the axial length of the mandrel is mounted and then printing plates are attached to the sleeve.
The sleeve is a cylindrical member molded of plastic or FRP or the like. The mandrel is pivotally supported by bearings at both ends thereof. Therefore, when the sleeve is mounted on the mandrel, the bearing of the handle-side of the mandrel is opened while holding the mandrel by the bearing of the drive-side in a canti-lever manner, and then a sleeve having the same axial length as the mandrel is inserted onto the mandrel from the open side. Blowout ports of air are formed in the mandrel; three at the both ends thereof respectively, three at the center thereof. Therefore, when mounting a sleeve to the mandrel, compressed air is sent into the mandrel so as to blow out air from the holes provided on the surface of the mandrel.
Since the inner diameter of the sleeve is substantially same as the outer diameter of the mandrel, an air layer is formed between the inner surface of the sleeve and the outer surface of the mandrel by air pressure. Hence, the insertion resistance of the sleeve is reduced, making it possible to push the sleeve easily up to the full width of the mandrel.
And then, the concave notch formed on the front end of the inserted sleeve is fitted to the convex portion provided on the surface of the mandrel, so that the positioning in the circumferential direction and axial direction of the sleeve on the mandrel is performed, restricting the movement of the sleeve in the circumferential direction and the axial direction at the same time. Finally, the filling of air into the mandrel is stopped.
Patent Document 1 discloses a manner for engaging the sleeve with the shaft, such as a mandrel. In the sleeve and flexographic printing axis of Patent Document 1, the diameter in the vicinity of both ends in the axial direction is different about 2 mm, respectively, being formed to be a so-called-conical shape with gentle slope. Thus the sleeve is engaged so as to be pressed and fixed to the flexographic printing shaft. Moreover, a key is provided on the inner surface of the sleeve, and in the outer surface of the flexographic printing shaft, a groove engaging with said key is formed. By the engagement of those key and groove, the positioning of the flexographic shaft and the sleeve, the restriction of slip in the circumferential direction are performed.
Furthermore, Patent Document 2 discloses a large bag accommodating a plurality of small bags in each of which toilet paper rolls, kitchen towels and tissue paper and so on are filled.